The finder of this coin wished to remain anonymous. It’s a gold stater, which has imagery on the reverse but the obverse is blank.
As is unusually the case, there is a horse on the reverse. The horse faces right, there is a ground line below and numerous symbols in the field. It dates from roughly 50 BC and in the Standard Catalogue it is listed under Gallo-Belgic issues as number 11.
In Ancient British Coins it is listed under Gallo-Belgic imports as the Gallic War Uniface type of the Ambiani (number 16). ABC says it is very common but whether or not you ever find a specimen depends on where you do your detecting. If you have access to areas where there was lots of Ancient Brutish activity then you stand a chance of finding one. If, like me, you only have access to land in West and North Yorkshire then the odds against you unearthing one are huge.
This stater is well and centrally struck and would grade good VF. If offered for sale at auction then a likely pre-sale auction estimate would be £500 – £600.